The French Canon de 75mm TR Saint-Chamond (Modele 1915) was strongly proposed for use on the Saint-Chamond gun carrier by Colonel Emile Rimailho, the cannon's designer and also the tank's technical director. The Saint-Chamond owes some its uncommon design and reputation for unreliability to housing a full-sized cannon, rather than shortened cannons as may be seen on the FT-17 and the first British tanks. This gun was later replaced by the earlier Canon de 75 modèle 1897, regarded as the first modern artillery piece due to its recoil-mitigating design.
Five ammunition types are available, of which two at most are used by the driver:
- Airburst (Gas Assault Package)
- This shell detonates a split-second after impacting a surface. The initial hit deals light damage, perhaps enough to wound infantry, but negligible to walls or armor. The bursting shell has a wide blast area, and can completely level a small structure.
- Case (Field Assault Package)
- Anti-infantry shrapnel shell.
- Gas (Gas Assault Package)
- Explosive shell containing poison gas. Does moderate damage to buildings, allowing the shell to fill the room behind a struck wall. A distinctive "gas escaping" sound plays when this shell is fired.
- HE Low Velocity (Field Assault Package)
- High explosive shell.
- HE High Velocity (Standoff Assault Package)
- High explosive shell fired with higher muzzle velocity.